Agricultural processing system and method

ABSTRACT

A method and device for processing an agricultural product is provided. The device includes a chamber having an opening, and a heater operative to heat the contents of the chamber. A sensor having an output is coupled to the chamber, the sensor output being processed to provide information about at least one of: a state of decarboxylation, or a quantity of a material in the contents of the chamber. The method includes loading a quantity of the agricultural product in a chamber having an port and applying an elevated temperature to the chamber to increase a rate of decarboxylation. A property of a gas is measured at the port the measurement being processed to determine one of either: a state of decarboxylation, or a quantity of material in the sample.

REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No.15/766,810, titled “AGRICULTURAL PROCESSING SYSTEM AND METHOD”, whichwas filed Apr. 7, 2018 as a national stage application under 35 U.S.C. §371, of International Patent Application No. PCT/US2017/069152, filed onDec. 30, 2017, each of which is incorporated by reference herein in itsentirety.

TECHNICAL FIELD

This disclosure generally relates to processing of agriculturalproducts, and more particularly to the decarboxylation or the assayingof agricultural products containing a cannabinoid.

DESCRIPTION OF RELATED ART

There are many different types of cannabinoid acids naturally occurringin agricultural products such as Cannabis sativa, certain types ofEchinacea, Acmella oleracea, Helichrysum umbraculigerum, and Radulamarginata. Naturally-produced cannabinoid acids include CBDA(Cannabidiolic Acid), CBGA (Cannabigerolic Acid), CBCA (cannabichromenicacid), and THCA (Tetrahydrocannabinolic acid), among others. The amountsof these acid forms of cannabinoids vary from plant to plant due togrowing conditions, genetics, harvest timing, and harvest techniques.Many cannabinoids derive increased therapeutic benefits bydecarboxylation of the acid form, thereby converting the cannabinoid toa neutral form, which is active in the body. Because the amount ofcannabinoids in a sample can vary substantially, knowing theconcentration of cannabinoid or cannabinoid acids is important to ensureproper dose control.

Measurement of neutral-cannabinoid or cannabinoid-acid concentration isconventionally determined using laboratory techniques such ashigh-performance liquid chromatography (HPLC); gas chromatography (GC);or diffuse reflectance near infrared (DRNIR) spectroscopy. However,these measurement techniques are generally performed on a raw sample,generally are performed using only a very small sample size, and arequite expensive. Knowing the quantity of a cannabinoid acid in a rawsample is somewhat useful in that it indicates the maximum potentialneutral cannabinoids that one could theoretically attain under perfectdecarboxylation conditions; however, the actual amount of neutralcannabinoids after processing, (e.g. cooking, vaporizing, converting toa tincture, smoking) is unknown without further measurements. For manyapplications the neutral form of the cannabinoid is the desired activecompound and therefore knowledge of the content of the original acidcannabinoids is of limited use. Sampling of cannabinoid profilesgenerally uses a very small quantity, on the order of a gram. As thecannabinoid content of a single plant (e.g. Cannabis sativa, Cannabissativa forma indica) may vary dramatically over the location on theplant (e.g. shaded portions of the plant may generate lowerconcentration of cannabinoids—variations of 20% are not uncommon) such asmall sample size provides only limited information as to the overallcannabis content. Furthermore the samples after processing for HPLC aregenerally unsuitable for consumption as the preparation includes mixingthe sample with a solvent and are therefore wasted. Presently availabletechniques are expensive at least in part because these techniquesrequire trained laboratory personnel and expensive lab equipment andreagents.

SUMMARY

Decarboxylation is a process in which a chemical change occurs to anacid-form of a molecule to convert it to a neutral form of the molecule.Application of an elevated temperature can accelerate thedecarboxylation process. When a cannabinoid acid is to be converted to aneutral form, complete conversion is desired as the cost of the startingplant material can be quite considerable.

For example, if a quantity of cannabis having 10 grams of CBDA is to beconverted to CBD and only half of the CBDA completes decarboxylation,then half of the material is wasted, as it remains in a non-bioavailableform. On the other hand, application of excess heat is undesirable asthe neutral forms of cannabinoids can start to degrade with furtherheating.

In accordance with an embodiment described herein, a system forprocessing an agricultural product comprises a chamber having anopening, a heater operative to heat the contents of the chamber, and asensor having an output, with the sensor coupled to the chamber. Thesensor output is processed to provide information about at least one of:a state of decarboxylation, or a quantity of a material in the contentsof the chamber.

In some embodiments the information includes information about thequantity of an acid-cannabinoid or a neutral-cannabinoid in the chamber.

The agricultural product may include: Acmella oleracea, Cannabis sativa,Cannabis sativa forma indica, Echinacea, Helichrysum umbraculigerum, orRadula marginata.

In some embodiments the sensor output is responsive to carbon dioxideconcentration, chamber pressure, a flow rate, or a temperature. Thesensor may include a pressure sensor, a bubbler, an orifice, acarbon-dioxide sensor, or an infra-red flow sensor.

In some embodiments the system further includes a valve.

The system may include a lid with a seal, with a pressure sensor coupledto the interior of the chamber via a port.

In some embodiments the system further includes a fan and a secondopening. The fan induces a flow from the second opening, past a heater,over the agricultural contents and out the first opening. The sensor maydetect carbon dioxide concentration at the first opening. A secondsensor responsive to carbon dioxide, located proximate the secondopening, may also be included.

The chamber walls may be insulated or comprise a vacuum flask; thechamber may have a thermally conductive lid.

In some embodiments a temperature sensor is coupled to the chamber. Aprocessor is coupled to the temperature sensor, and the sensor having anoutput coupled to the chamber is a pressure sensor. The processorcontrols the chamber temperature to vary between at least twotemperatures while monitoring the pressure. The processor processesthese data to detect a property of at least two different cannabinoidsin the chamber.

In accordance with an embodiment described herein, a method forprocessing an agricultural product comprises loading a quantity of theagricultural product in a chamber having an port; applying an elevatedtemperature to the chamber to increase a rate of decarboxylation;measuring a property of a gas at the port; and, processing themeasurement to determine one of either: a state of decarboxylation, or aquantity of material in the sample.

An additional step of sealing a lid may be included, after the step ofloading a quantity of the agricultural product. The lid remains sealeduntil the temperature returns to ambient conditions. In this embodiment,the step of measuring a property of the gas at the port is a pressuremeasurement.

An additional step of sealing a lid may be included, after the step ofloading a quantity of the agricultural product. The lid remains sealeduntil the temperature returns to ambient conditions. In this embodiment,the step of measuring a property of the gas at the port is a mass-flowrate from the chamber to the ambient through a port.

In some embodiments the lid isn't sealed, and the step of applying anelevated temperature to the chamber comprises forcing air from an inputport past a heating element into the chamber.

In some embodiments the step of measuring a property of the gas at theport comprises measuring carbon dioxide concentration. In someembodiments an additional measurement of carbon dioxide concentration atthe input port is used.

In accordance with an embodiment described herein, a system forprocessing an agricultural product comprises a chamber having anopening. A heater, operative to heat the contents of the chamber, iscoupled to the chamber. A first sensor having an output is coupled tothe chamber, as is a temperature sensor having an output. A processorhaving first- and second-inputs and an output is coupled to thefirst-sensor output and the temperature-sensor having an output. Theprocessor output is coupled to one of either a valve, or the heateroperative to heat the contents of the chamber. The first sensor outputmay be responsive to at least one item selected from group consistingof: carbon dioxide concentration, chamber pressure, a flow rate, and atemperature.

BRIEF DESCRIPTION OF DRAWINGS

The figures listed below illustrate exemplary embodiments, and are notintended to cover all possible embodiments, including embodiments withadditional or fewer components, steps, or connections. The embodiments,techniques, components, connections, and other teachings described inthe figures are exemplary and were chosen to provide a clear explanationwithout unnecessary obfuscation.

FIG. 1 illustrates a schematic diagram of a first embodiment of adecarboxylator.

FIG. 2a illustrates a schematic diagram of a second embodiment of adecarboxylator with a heating tube.

FIG. 2b illustrates a schematic diagram of a third embodiment of adecarboxylator with a thermally-conductive plate.

FIG. 3 illustrates a schematic diagram of a decarboxylator having athermally isolated cover.

FIG. 4 illustrates a schematic diagram of an exemplary mass-flowdetection system.

FIG. 5 illustrates a fourth embodiment of a decarboxylator.

FIG. 6 illustrates various state variables as an empty chamber washeated.

FIG. 7 illustrates a fifth embodiment of a decarboxylator comprising asealed chamber.

FIG. 8 illustrates a sixth embodiment of a decarboxylator comprising aforced-air heater.

DETAILED DESCRIPTION

Plant material loaded into a decarboxylation chamber, or simply achamber, is hereby termed a charge, or a charge of material. The amountof time required for complete decarboxylation of the charge depends onat least the temperature. Excessive heat applied to the charge causesdegradation of cannabinoids into other compounds different than thedesired active compound, as well as excess loss of terpines. Materialhaving differing density can have different thermal time constants inthe chamber as well; therefore, it is difficult to determine whendecarboxylation is complete by just monitoring and/or controlling thetemperature of a decarboxylation chamber.

In some embodiments a vacuum flask, or Dewar flask, similar inconstruction to a vacuum-insulated food jar conventionally used forkeeping packed lunches warm, is used as a decarboxylation chamber. Invarious embodiments the chamber comprises metal, glass, coated glass ormetal, or glass having at least one mirror-like surface. Unlike achamber insulated with foam, fiberglass, or other material, a vacuumflask includes at least a partial vacuum between an inner chamber walland an outer wall, thereby removing thermal conduction (in accordancewith the quality of the vacuum) as a potential thermal-loss mechanism.Since thermal radiation is quite low at normal decarboxylationtemperatures the heat loss from the chamber becomes quite small allowingfor a fast thermal time constant and a more uniform chamber temperature.Providing heat from the internal portion of the vacuum flask, as opposedto between the inner chamber and outer wall, improves manufacturabilityand thermal performance as the heating element doesn't have to includeany portion in the vacuum space between the inner-chamber wall and theouter-chamber wall; including components in this region can result inoutgassing, thereby reducing vacuum, as well as provide additionalthermal conduction paths. In some embodiments the chamber includes a topcomprising a heater, and a seal between the top and the chamber wherein,after the charge is loaded into the chamber, the top is affixed to thechamber (e.g. by screw, clamp, etc.) thereby providing an airtight seal,allowing carbon dioxide, water vapor, or other gasses to be quantifiedas they leave a port as described later. In various embodiments the sealcomprises neoprene, EPDM, silicone, an elastomer, a plastic, rubber, agasket, a metal gasket, a crush gasket, or any other suitable material.In various embodiments the lid comprises a thermally conductivematerial, for at least a portion of the lid, such as aluminum, copper,iron, or steel.

FIG. 1 illustrates a first embodiment of a decarboxylator. Top 101comprises a heating plate 103 that faces into the chamber 105 of vacuumflask 107. Vacuum flask 107 comprises an outer shell or wall 121, aninner wall 111, and an evacuated space 119; the outer and inner wallsmeet at lip 123. Heating plate 103 is made from a thermally conductivematerial, for example: copper, steel, or aluminum. Heater 109,comprising a resistive element or Peltier device, is located on theopposite side of the heating plate and is thermally coupled to theplate. In some embodiments thermal coupling includes thermal grease toimprove heat transfer characteristics, a mechanical clamp that holds theresistor in contact with the heating-element plate, or a combinationthereof. In some embodiments a thermal bridge between the top or heatingplate and the inner chamber walls is formed when the top is affixed,thereby transferring heat from the heater to the inner wall 111 of thevacuum flask 107 with a low thermal resistance. In particular, a vacuumflask with an inner wall made of metal will conduct heat effectivelyfrom plate 103 through the inner wall 111, thereby completelysurrounding the charge with an approximately equal temperature. Forexample, in some embodiments the plate extends to a screw 113 (e.g.threaded portion) that makes contact with the inner chamber wall 111when the lid is closed; a thermal bridge may also be formed using ametal spring or brush affixed to the heating element plate that makescontact with the inner vacuum-flask wall upon closing. Top 101 alsoincludes a port 115 coupled between chamber 105 and the atmosphere. Theport, which may be a narrow metal tube, provides a path for gassesgenerated or expanded (e.g. by heating) inside chamber 105 to leave thechamber for mass detection, as described later. Seal 117 prevents gassesfrom leaving the chamber via a path other than the port.

Note that seal 117 doesn't prevent gasses, such as air, from leaving orentering the chamber, but rather seal 117 limits the path by whichgasses enter or leave the chamber to port 115 so that they may bequantified, or that a positive- or a negative-pressure doesn't build upbeyond a threshold in the chamber. In some embodiments, allowing gassesto freely exchange into and out of the chamber purges oxygen from thechamber due to thermal expansion, or due to displacement with generatedcarbon dioxide and steam vapor. For example, simply by heating air froma temperature of 25 C to 100 C will cause about 20% of the oxygen toleave the chamber through the port due to the expansion of the oxygenaccording to the ideal gas law. Furthermore, moisture in the charge,which may average about 5% to 10% by weight is converted to steam atapproximately 100 C further displacing oxygen from the chamber. Forexample, given a charge mass of 25 grams that occupies a volume of 500ml, a 5% moisture content would result in about 1.5 liters of watervapor (e.g. steam), which will purge the oxygen from the chamber as thewater vapor leaves the port. Thus, allowing gases to escape through aport removes oxygen from the chamber to a level below the initial valueat a point of sealing providing a lower oxygen content. On the otherhand, the temperature will fluctuate during the decarboxylation process,which can cause positive or negative pressure to build up if gasexchange is prevented. Thus, in some embodiments air, or ambient gassescontaining oxygen, enters the chamber via the port while the charge orchamber is at an elevated temperature, for example as the chambertemperature dips during a temperature cycle. However, oxygen that entersthe chamber during the decarboxylation process via the port is quicklypurged, as water vapor or the carbon dioxide generated from thedecarboxylation process itself purges the oxygen from the chamber.

In another embodiment, with reference to FIG. 2a , top 201 comprises aheating tube 203 that protrudes into the chamber 205; top 201 may bemade of an insulating material such as plastic or a thermally-conductivematerial such as metal. Heating element tube 203 is made from aconductive material such as copper, steel, or aluminum. A heatingelement, 207, which may comprise e.g. a resistor, or a nonlinearresistor such as a tungsten filament, a Ni-Chrome wire, or a light bulb,is located internal to heating element tube 203 and is electricallyconnected to the tube at the end 209; in some embodiments the heatingelement is electrically connected to a first insulated wire (not shown)instead of the tube at the end. Thermal grease, 211, which in someembodiments includes a zinc oxide or aluminum oxide filler material, isplaced in the space between the resistor and inner heating-element tubewall thereby providing a low thermal-resistance path to the tube wall.The other end of heating element 207 is connected to a second wire 213,which may include insulation to prevent incidental contact with theheating element tube wall. The wire, in conjunction with an additionalelectrical connection to the heating element tube 215 (or insulated wirewhen a connection to the tube end is not used), are the terminals forthe heater and are controlled by a processor 217, which controls theheater via a relay, transistor, switch, GPIO, or any other suitablemechanism. Heating element tube 203 also includes inside one or moretemperature measuring devices 219, such as a thermocouple or athermistor, which may be used to control the temperature using afeedback loop by the processor. In some embodiments the feedback loop isan analog feedback loop not involving a processor (e.g. a feedback loopconstructed using one or more opamps or comparators). In someembodiments the temperature-measuring device is located at a differentlocation, internal to the decarboxylation chamber, than the heatingelement tube, such as protruding from the lid, or recessed into the lid.A thermal fuse or thermal switch may be included in series with theheating element to prevent a hazardous fault condition: if thetemperature at the thermal fuse or thermal switch rises above the ratedfuse temperature the flow of electricity through the heating element isstopped thereby preventing overheating of the charge or reducing a firehazard.

With reference to FIG. 2b , in some embodiments a thermally-conductiveplate 251 (e.g. copper, aluminum, steel) is coupled to the heating tubebelow a bottom surface 253 of the top. Plate 251 provides alow-resistance thermal path in the radial direction of the chamber,thereby reducing thermal gradients caused by conduction through thebottom surface 253 of the top. An insulating layer 255 (such as an airgap, foam, or plastic) between plate 251 and surface 253 providesthermal insulation. While heat is lost though surface 253 at a ratesubstantially higher than through a vacuum, the thermal conductivity ofe.g. copper is about 16,000 times higher than, e.g. air. Therefore,thermal gradients are minimized. In some embodiments a portion of theheating tube 261 is exposed to ambient conditions so as to provide asource of thermal loss for a class-A-style biasing scheme. Alternately,instead of directly exposing a portion of the heating tube to ambient, aclass-A-style bias condition may be effected by choosing an insulationthickness to place on top of the portion of heating tube 261 thatprovides the desired heat loss characteristic.

Since a vacuum flask is an excellent insulator the chamber will remainat an elevated temperature for an extended period of time after theheater has been de-energized. In various embodiments a Peltier devicecoupled to the heating element tube or heating plate is used to cool thechamber after decarboxylation has completed; an alarm is sounded (i.e. abeep) to indicate the material should be removed; a vent is openedallowing circulation of room-temperature air through the chamber; or afan is energized or remains energized upon completion. In someembodiments the heat input to the decarboxylation chamber is reduced inanticipation of complete decarboxylation as the decarboxylation nearscompletion so the chamber temperature is below a temperature thresholdonce decarboxylation has completed.

In some embodiments the lid or top comprises metal and includes a meansof cooling to ambient conditions after heat ceases to be applied to themetal e.g. a radiator, a fan, an exposed, thermally-conductive surface(e.g. portion 261 of tube). By providing a way for the chamber to cooltowards ambient temperature, the heat flow is effectively biased akin toa class-A amplifier in electronics: chamber temperature may be increasedor decreased about the present temperature by controlling the amount ofheat added to the lid in this embodiment. Cooling relative to thepresent temperature of the lid is accomplished not by actively removingheat from the lid but rather reducing the amount of heat added to thelid.

In some embodiments, as illustrated in FIG. 3, a lid 301 with a metaltop 303 comprises a heater 305; and, a seal 307 makes contact with thechamber and prevents gasses from escaping at the interface therebyensuring they leave through the port 309. Port 309 is connected to aflow measurement system outside of the chamber. Thermal bridge 311, inthis case metal threads in the lid that interface with metal threads onthe inner chamber wall, provides improved and more-even heating of thechamber walls and, thus, charge. In some embodiments a conductive tubeas previously described or a passive tube made of metal without anyheating elements is used to conduct heat towards the center of thechamber. Since the temperature of the lid can be in excess of 100degrees C. a thermally isolated exterior cover 321 (e.g. made fromplastic) is coupled to the lid thereby preventing direct contact of thephysical lid by a user, improving safety, as well as reducing thermalloss from the top to ambient.

In some embodiments the quantity (e.g. mass) of gasses released duringthe decarboxylation process is determined and this quantity: is used toestimate the amount of cannabinoids in a sample; is used to determine astate of decarboxylation; or, is used for both purposes. As a singlemolecule of, e.g., CBDA is decarboxylated into CBD a single molecule ofcarbon dioxide (CO2) gas is released in the process. Relating the amountof CO2 released to the amount of neutral cannabinoids decarboxylated maybe performed using stoichiometry; alternately, a functional relationshipmay be established between the acid form of the molecule, the neutralform of the molecule, and the amount of CO2 released, for example byexperimental measurements of released CO2 from a plurality of referenceplant materials decarboxylated in the chamber at an elevatedtemperature, and calibrated by pre- and post-decarboxylation HPLC testresults in combination with a regression analysis.

As an example, using stoichiometry it may be found that CBDA has anapproximate molar mass of 358 g/mol and the neutral form CBD has anapproximate molar mass of 314 g/mol; the product of the reaction, CO2,has a molar mass of 44 g/mol. Thus, if we determined that 1 gram of CO2was released during the decarboxylation process that would indicate that7.1 grams of CBD were decarboxylated per the following relationshipbetween CO2 and CBD determined by stoichiometry:

grams of neutral CBD=(1 gram of CO2/(44 grams/mol of CO2))*(314grams/mol of CBD)

Therefore, the amount of acid-cannabinoid decarboxylated to the neutralform may be determined by quantifying the mass of released gasses duringdecarboxylation and mathematically operating, or processing, thisquantity. Alternately, or in addition, by monitoring the evolution ofgasses when the charge is at a decarboxylation temperature, completionof the decarboxylation process may be determined, (e.g. by adetermination that gas generation has dropped below a threshold, a rateof pressure increase in a closed chamber less than a threshold, or a gasflow rate below a threshold). Measurement of released gasses may be usedto control the temperature over time in the decarboxylation chamber toensure complete decarboxylation; quantifying the gasses released duringthis process allows a calculation of the total amount ofacid-cannabinoids in the initial sample, or alternately the amount ofneutral cannabinoids in the decarboxylated sample formed during thedecarboxylation process. When combined with the mass or volume of thecharge (e.g. measured by a scale or a known volume, such as acup-measure used for cooking) a percentage by weight or volume may bedetermined, thereby allowing more accurate dosage to be determined. Ingeneral while the preponderance of cannabinoids found in raw plantmatter are of the acid form, there may exist small quantities of neutralforms of these cannabinoids. Generally these quantities are small, oftenless than 1% of the total mass of flowers versus up to greater than 30%for the acid form of cannabinoid.

In some embodiments a mass-measuring sensor such as a load cell iscoupled between a base and the outside of the decarboxylation chamber.The weight of the decarboxylation chamber is borne by the load cell. Theload cell is tared or zeroed before the charge is loaded and measuredagain after the charge has been loaded allowing calculation of the massof the charge.

Quantification of mass of gasses released may use any suitable methodincluding mass inference using at least one of: chamber pressure,carbon-dioxide concentration, chamber temperature, atmospheric pressure,differential pressure, differential pressure across an orifice, gaugepressure, absolute pressure, temperature, a thermal mass-flow meter,volume-flow rate, or mass flow.

By monitoring the evolution of gasses from a decarboxylation chamber thepresent state of the decarboxylation process may be determined, as gasgeneration rate is directly dependent on the rate of decarboxylation ofthe acid compound. For example, upon reaching a decarboxylationtemperature, which may or may not be precisely controlled, the rate ofgas generation from the chamber is monitored. In some embodiments, thetemperature is not directly regulated: the rate of heat addition intothe decarboxylation chamber is instead controlled by the rate of gasgeneration in the chamber, or the rate of change of the rate of gasgeneration in the chamber, to maintain a target gas generation ratewhich changes over time as the charge becomes fully decarboxylated. Theaddition of heat to the chamber is constrained so the chamber operateswithin an operating temperature region to prevent the chambertemperature from reaching an undesirable temperature (for example, heatmay be added to the chamber as needed to maintain a certain CO2 flowrate as long as the chamber temperature doesn't rise above 130 degreesC.).

Over time there will be less cannabinoid acid to decarboxylate, as ithas already been converted to neutral form; therefore, the rate of gasgeneration will decrease. When the decarboxylation is sufficientlycomplete the rate of gas generation will drop below a thresholdindicating completion of the process.

In some embodiments the rate of gas generation for an initial quantityof a first cannabinoid acid at a constant temperature follows a firstfunctional relationship (e.g. exponential, quadratic, cubic, linear)between time and gas generation rate; this first functional relationshipalso being dependent on temperature. Such a functional relationship maybe determined by regression analysis of calibrated plant material (e.g.via HPLC) using a design-of-experiments process including time andtemperature as variables.

In some embodiments the rate of gas generation for an initial quantityof a second cannabinoid acid at a constant temperature follows a secondfunctional relationship (e.g. exponential, quadratic, cubic, linear)between time and gas generation rate; this second functionalrelationship also being dependent on temperature and also being adifferent functional relationship than the first functionalrelationship.

In some embodiments the charge includes at least two distinctcannabinoid acid forms (e.g. CBDA, THCA) each having a differentfunctional relationship. By measuring the gas generation rate at a firstknown temperature (e.g. using a thermocouple) and the gas generationrate at a second known temperature the relative composition (e.g.percent concentration, apportionment of mass) of the cannabinoid acidsin the sample may be inferred using the known first and secondtemperatures, the known first- and second gas-generation rate functionalrelationships, the measured gas generation characteristics, and the timehistory of these variables (e.g. time and temperature), for example bysolving a system of equations expressing these relationships andquantities.

In some embodiments mass flow is inferred using a differential pressuremeasurement across an orifice, or a Venturi tube. In some embodimentsmass flow is inferred by counting bubbles generated in a bubbler such ascommonly used as an airlock to prevent microbial contamination whenhome-brewing beer; counting may use optical detection of movement (e.g.camera or breaking a light beam between a light source and a lightdetector), a magnet with a switch or sensor, an acoustic sensor, anaccelerometer or any other appropriate sensor.

In some embodiments, mass is determined using a pressure sensor andvalve where the valve is closed and the pressure is sampled with thevalve in the closed position. Next, after the pressure reaches athreshold the valve is opened releasing the pressure. Because the volumeand pressure before the valve is opened and after the valve is closedare both known, the mass lost through the valve when opened may beestimated using, for example, the ideal gas law. In some embodiments therate of pressure rise between valve events (e.g. an open, a close) isused in conjunction with the ideal gas law, and a known chambertemperature to determine the mass generation rate of the gasses (e.g.using a direct pressure-rate calculation given two times and pressurevalues; using a measurement of the time between valve opening eventsgiven a pressure threshold at which point the valve is opened; using acount of the number of valve opening events, etc.). In some embodimentsthe valve is normally open and periodically closed for a time-periodduring which the pressure is monitored. After a time-period has elapsedthe pressure is sampled and the valve opened; given the initial andfinal pressures and temperature over this sampling time thegas-generation rate may be determined using e.g. the ideal gas law. Insome embodiments a calibration step is performed to improve accuracy ofa mass measurement device by starting the empty decarboxylation chamberat a first known temperature, heating the chamber to a second knowntemperature, monitoring the mass flow rate through a port, andtotalizing the mass flow; the ideal gas law provides the relationship ofthe initial air mass lost given the initial and final temperature andthe chamber volume; this quantity is used to calibrate the mass flowsensor output.

As the chamber cools a negative pressure may form, meaning the chamberpressure may be lower than atmospheric pressure; this can make openingthe chamber difficult, or damage a pressure sensor. To prevent excessnegative pressure from forming, in some embodiments a second, passivevalve is included providing a path for air to enter the chamber when thepressure of the chamber is below the atmospheric chamber, for example asthe chamber cools air would enter the chamber through a one-way valvethereby preventing the water in the case of a bubbler, from being suckedinto the chamber. Alternately a solenoid valve may be placed in the openposition when the chamber pressure is detected as negative or thechamber is being cooled.

In some embodiments the mass flow is derived using a volumetric flowthat quantizes gas volume with an unknown scale factor supplemented witha measurement of mass. For example, an un-calibrated airlock-bubblercommonly used for at-home beer brewing is used to measure volume of gasreleased from the chamber. To make use of such an un-calibrated flowmeasurement the mass of the charge is measured before placement in thechamber and again after the decarboxylation process has completed. Theweight post-decarboxylation will be less by the amount of any watervapor driven off as the cannabis was heated to above the boiling pointof water, and the reduction in mass due to the carbon dioxide releasedin the conversion of the cannabinoid-acid to the corresponding neutralform. While the two gasses have different molecular weights the watervapor is driven off around 100 degrees C., as the vapor pressure ofwater is 1 atmosphere at this condition and the CO2 is driven offsubstantially faster at higher temperatures. Thus, given two knowngasses (water vapor and carbon dioxide) which are released at differentrates at different temperatures, the total mass lost as measureddirectly by a scale may be apportioned between moisture and carbondioxide by the integral of the flow meter output in conjunction with aknown temperature of the charge during the time that the volumetric flowmeasurements were taken using a system of linear or linearizedequations. In some embodiments the charge is first thoroughly dried, forexample in a desiccation chamber using calcium chloride as a desiccant.By removing moisture from the charge all gasses released during thedecarboxylation cycle will be carbon dioxide, the molecular weight ofwhich is known. In some embodiments the gasses from the port are cooledto a known temperature before entering the volumetric flow meter, or thetemperature is measured, so that the volumetric flow rate may accountfor the variable density of gas over temperature thereby maintainingaccuracy in mass-flow estimation.

FIG. 4 illustrates a schematic diagram of an embodiment of a mass-flowdetection system. Input 401 is coupled to the interior of thedecarboxylation chamber (e.g. via port 115 or 309) so that gassesgenerated during the decarboxylation process may flow into the mass-flowdetection system. Input 401 is further coupled to T-junction 403 coupledin turn to both pressure sensor 405 and valve 407. Valve 407 may be anormally-open or normally-closed valve and is controlled using anelectrical signal 409 generated using processor 411 and, optionally, arelay or transistor. When open, valve 407 allows gasses at the input ofvalve 407 (e.g. at T-junction 403) to couple to the atmosphere via vent415. Processor 411 monitors the output 413 of pressure sensor 405; uponreaching a pressure threshold, processor 411 activates the valve viaelectrical signal 409 thereby dropping the pressure. A variable on theprocessor is used to maintain track of the number of times the valve wasopened, the pressure drop when the valve opened and then reclosed, or acombination thereof. Alternately, processor 411 maintains valve 407 inthe open position and periodically closes the value while monitoring thepressure when the valve is closed. Gas generation rate is determined inthis case by the increase in pressure versus time; after a period ofmeasurement the valve is returned to the open state. A variable on theprocessor is used to maintain track of the number of times the valve wasopened, or the pressure drop when the valve closed and then reopened;these measurements are combined to account for the total amount of gasreleased between instants of measurement, using for exampleinterpolation, extrapolation, integration, or totalization.

FIG. 5 shows a decarboxylation chamber with a lid having processing andcontrol circuitry. Chamber 501 has an inner wall 503 and an outer wall505 separated from each other with a vacuum space; the inner and outerwalls are formed of metal (e.g. stainless steel) and are attached at therim 507; in some embodiments the inner and outer walls are attached to amaterial having lower thermal conductivity than the materials 503 and505 (e.g. A phenol-formaldehyde resin) as opposed to directly incontact. Lid 509, comprising a thermally-insulating material such as aplastic, is coupled at coupling point 539 (using e.g. a screw, a rivet,a clasp, a barb, an adhesive, etc.) to thermally conductive plate 511and an optional thermally conductive tube 513 that protrudes into thedecarboxylation chamber thereby improving heat transfer characteristics.The conductive plate 511 makes physical contact with threads 515 in theinner wall 503 thereby forming a thermal bridge allowing heat to betransferred from the conductive plate to the inner chamber walls. Thetemperature of plate 511 is measured with temperature sensor 517 (e.g. athermocouple, thermistor, diode) the output of which is coupled toprocessor 519. In some embodiments the temperature sensor is located intube 513, on plate 511, or multiple temperature sensors are used tomonitor or control the temperature uniformity throughout the chamber.Heat is applied to the conductive plate 511 or tube 513 using adissipative element such as a resistor or a nonlinear resistor 521thermally coupled to either plate 511 or tube 513 using a mechanicalinterface (e.g. clamp, physical contact), a thermal grease, or acombination thereof. Processor 519 is coupled to a circuit board 539,and receives an input from the temperature sensor through cable 535(comprising a plurality of conductors) and controls energy to theheating element 521 using an output such as ageneral-purpose-input-output pin (GPIO pin) coupled to a transistor or arelay, as processor outputs generally have insufficient drive capabilityto energize a heater of more than a fraction of a Watt directly. Theprocessor further monitors the pressure inside the chamber 501 via aport 523 (e.g. metal tube, silicone tube) that couples the inner chamberto pressure sensor 525. Processor 519 also is coupled to valve 527 that,when opened, provides a path for gasses under greater than ambientpressure to escape from inside the chamber. During the decarboxylationprocess the pressure is monitored and the valve is controlled in concertwith the output of the pressure sensor to monitor or quantify the rateof gas generation within the chamber by the charge in a manner similarto that described earlier. Because tube 513 or plate 511 may get hotduring operation the operator is shielded from direct contact by aninsulating guard 541 made of a material having lower conductivity thanthe tube or plate, such as a thermoset plastic. Guard 541 also providesa mechanical structure for supporting (e.g. by screws, snaps) variouscomponents such as a pressure sensor, a valve, a processor, etc. in thelid at a temperature lower than the temperature of the tube or platethereby improving reliability and performance of the components. In someembodiments a fan 529 (e.g. a fan similar to a fan used for cooling amicroprocessor) is energized as appropriate by the processor to maintaina component (e.g. processor, sensor, actuator) below a maximumtemperature. In some embodiments the fan is energized to increase therate of cooling of plate 511 or tube 513, or to apply a thermal (e.g.heat) bias similar to a class-A amplifier in electronics. Insulation 537above plate 511 provides an additional degree of freedom to control theheat loss from the chamber, in conjunction with fan control, as well asreduce the amount of heat transferred to the electrical components.Input grille 531 and output grille 533 provide input and output vents socool air may be circulated by the fan 529 past the electronics, and thenpast the top or tube. Seal 543 makes contact between the lid and thechamber rim thereby forcing any gas exchange to occur through the port523.

FIG. 6 shows measured temperature in Celsius (601), pressure in kPa(603), and valve position (605) where 0 indicates a closed valveposition with the valve otherwise open, as an empty, one-pint volume washeated from room temperature to an elevated temperature. A processor wasconfigured to monitor the pressure and open the valve for 0.5 secondswhen the pressure reached 0.7 kPa gauge pressure, thereby releasing thepressure. As can be seen from FIG. 6 the valve was opened about 33 timesas the temperature rose from ambient to about 83 degrees C. In thisexample the valve was only opened for 0.5 seconds, so the pressuredoesn't drop fully to ambient; therefore, the amount of mass removedduring the release portion of the cycle may be more accurately estimatedusing the pressure before the valve is opened, the pressure after thevalve is closed, and the chamber temperature to determine the amount ofgas (e.g. mass, or mole fraction) released during the time the valve isopen using the ideal gas law. Furthermore, as the temperature rises, themass of gas released per release cycle (e.g. every time the pressurereaches 0.7 kPa the valve is opened to release gas), will drop becausethe density of a hot gas is lower than a cool gas. Accurate massestimation takes the varying density of the released gas overtemperature to provide a more accurate estimate of mass of the releasedgasses, accounting for the fact that the density of gas released overtemperature is variable function of temperature.

With reference to FIG. 7, in some embodiments the gas generation isinferred using a closed pressure vessel 701, having a pressure sensor703, as the decarboxylation chamber. The charge is placed in the chamber711, the lid 705 is sealed with a seal 707, the chamber heated to adecarboxylation temperature above 100 degrees C., and the pressuremonitored. An optional safety valve 709 opens when pressure exceeds thedesign capacity of the chamber providing protection in the event of anoverpressure condition. The chamber walls 713 may be of a double-walledconstruction with an insulated interior, such as a vacuum flask, withheat applied via a heated portion of the lid or a thermally-conductivetube protruding into the chamber; alternately, the chamber walls 713 maybe of a solid construction, e.g. aluminum, suitable for conductingexternally provided heat such as a household or commercial oven. Afterthermal equilibrium has been reached in the chamber there will be acomponent of the pressure that is due to moisture in the charge; thiscomponent is a function of the vapor pressure of water at temperatureand does not increase during the decarboxylation process. However, asdecarboxylation generates carbon dioxide the chamber pressure will rise.After the decarboxylation process has ceased, as determined by thechange of pressure over time dropping below a threshold, the containeris cooled back to the same temperature at which it started. The pressureis noted and, in conjunction with the known volume of the chamber,indicates the amount of carbon dioxide gas generated during thedecarboxylation process according to (deltaPV/RT)=n where n is thenumber of moles of CO2 gas created. Since each molecule of CO2 releasedcorresponds to a molecule of cannabinoid acid being converted to theneutral form the total number of molecules, and hence mass, of convertedacid-cannabinoid may be estimated given the molecular weight of thetarget cannabinoid. In some embodiments the initial and finaltemperatures are different and are compensated for using measured valuesof the initial and final temperatures in conjunction with the ideal gaslaw. After measurement, the pressure is released using a release valvecoupled to the chamber (e.g. via the pressure sensor, the safety valve,or an additional valve for this purpose) and the container opened. Thusthe acid-cannabinoid has been fully decarboxylated and the amount ofacid-cannabinoids converted to the neutral form quantified.

With reference to the schematic diagram of FIG. 8, in some embodiments afan 801 blows air in a direction 825 past a heating element 803 into adecarboxylation chamber 805; the air is filtered in some embodiments bya HEPA filter 821. In some embodiments a non-oxidizing gas such as drynitrogen or argon is used in place of air as an input to heating element803. In some embodiments the air is heated in a manner similar to ahousehold hair-dryer, with an electrical filament; however, largercommercial or industrial-scale decarboxylation operations may use anysuitable manner for providing heat, such as natural gas, an electricalfurnace, heat pump, waste steam, etc. Plant material to bedecarboxylated is placed on trays 807 having a mesh bottom therebyallowing the heated air to penetrate the plant material. Baffles 819help evenly distribute the air across the chamber thereby ensuring moreeven decarboxylation. The output of the chamber is vented through anexhaust port 811. In some embodiments the chamber walls 823 areinsulated using foam, fiberglass batting, vacuum like a Dewar flask, orany other appropriate insulation. The hot air, typically having atemperature greater than 100 degrees C., is blown by or through theplant matter causing decarboxylation to occur, thereby releasing carbondioxide in the process. A first carbon dioxide detector 813 measures thecarbon dioxide concentration at the port and determines decarboxylationis complete when the carbon dioxide level drops below a threshold, e.g.500 ppm. In some embodiments a second carbon dioxide sensor 815 isplaced in the air flow before the decarboxylation chamber so that theamount of CO2 generated by decarboxylation may be determinedirrespective of the ambient CO2 levels which may vary, especially inenclosed spaces. In some embodiments the CO2 sensor has a full-scalevalue of 0.1% to a few percent CO2 and uses infrared radiation to detectCO2 for example a nondispersive infrared sensor. The first and secondCO2 sensors are zero-calibrated by measuring the CO2 sensor outputs withan empty chamber; since no CO2 is being generated between the first andsecond sensors and the difference between the two sensors may be used tozero or tare the measurement of CO2 generation in the chamber. In someembodiments the air at the output of the chamber is sampled with a tube,the tube cooling the exhaust to near the input temperature to avoidtemperature sensitivity of the CO2 sensor from adding errors to themeasurement. Measurement of the carbon dioxide level at the port, inconjunction with the mass flow rate of the exhaust gas at the outputallows the amount of carbon dioxide generated during the decarboxylationprocess to be integrated allowing the amount of acid-cannabinoidconverted to the neutral form to be calculated. In conjunction with theinitial or final mass of the plant material, a percentage ofneutral-form cannabinoid may thus be calculated. Mass flow rate at theexhaust port may be accomplished using a differential pressure sensorand a Venturi tube, a turbine flow meter, an assumed density of air, ameasurement of the temperature at the exhaust port, or any otherappropriate method for measuring flow.

In some embodiments a fat such as clarified butter, coconut oil, cacaobutter, etc. is placed in the chamber with the charge. Inclusion of afat or oil with the charge allows cannabinoids to be dissolved in thefat or oil during decarboxylation after which the fat or oil is drainedfrom the plant matter and is ready for use.

The embodiments, techniques, components, connections, and otherteachings described herein are examples and were chosen to provide aclear explanation without unnecessary obfuscation. The scope of coverageis not intended to be limited to the specific exemplary teachings setforth herein, but rather the scope of coverage is set forth by theclaims listed below.

I claim: 1) A system for processing plant material comprising: a chamberhaving a first opening and a second opening; a heater operative to heatcontents of the chamber; a first carbon-dioxide sensor having an output,the first sensor coupled to the chamber; and, a fan coupled to thechamber and configured to provide a flow of gasses from the firstopening through the chamber and out the second opening. 2) The system ofclaim 1 wherein the carbon-dioxide sensor is a non-dispersive infraredcarbon-dioxide sensor. 3) The system of claim 1 wherein the sensoroutput is processed by a processor to indicate at least one selectedfrom the following list: whether decarboxylation is complete to within athreshold; an estimated quantity of released carbon dioxide; anestimated quantity of a neutral cannabinoid; or, an estimated quantityof an acid cannabinoid. 4) The system of claim 1 further including: amass-flow sensor configured to indicate a flow of gasses through thechamber; wherein the mass-flow sensor output is processed by a processorin combination with the carbon-dioxide sensor. 5) The system of claim 4wherein the mass-flow sensor uses temperature to detect or quantifyflow. 6) The system of claim 1 wherein the fan is coupled between anambient and one of either the chamber's first or second opening. 7) Thesystem of claim 1 wherein the fan and heater are coupled between anambient and the chamber. 8) The system of claim 3 wherein the heater isde-energized in response to a result obtained by processing of thesensor output. 9) The system of claim 1 wherein the heater isde-energized in response to a carbon dioxide concentration below athreshold. 10) The system of claim 1 further including: a secondcarbon-dioxide sensor having an output; wherein the first carbon-dioxidesensor is coupled to the second opening; wherein the secondcarbon-dioxide sensor is coupled to the first opening; and, wherein adifference is calculated between the first and second carbon-dioxidesensor outputs by a processor. 11) The system of claim 1 wherein thecoupling of the carbon-dioxide sensor to the chamber further includescooling of the gasses before being presented to the sensor. 12) Thesystem of claim 1 wherein the chamber further includes an exhaust portand the coupling of the first carbon-dioxide sensor to the chamberincludes coupling of the first carbon-dioxide sensor to the exhaustport. 13) A system for processing plant material comprising: a chamberhaving a first opening and a second opening; a heater operative to heatcontents of the chamber; a first carbon-dioxide sensor having an output,the sensor being coupled to the chamber proximate the first opening; asecond carbon-dioxide sensor having an output, the sensor being coupledto the chamber proximate the second opening; a mass-flow sensor havingan output, the mass-flow sensor coupled to the chamber; and, a fancoupled to the chamber and configured to provide a flow of gasses fromthe first opening through the chamber and out the second opening. 14)The system of claim 13 further including: a processor coupled to thefirst carbon-dioxide sensor output, the second carbon-dioxide sensoroutput, and the mass-flow sensor output; and, wherein the processor isconfigured to process the outputs to provide information about aquantity of a cannabinoid; a quantity of a cannabinoid acid; whetherdecarboxylation is complete to within a threshold; or, an estimatedquantity of released carbon dioxide. 15) The system of claim 14 whereinthe heater is de-energized in response to a result obtained byprocessing of the sensor outputs. 16) A method for processing plantmaterial comprising: providing a quantity of material, the materialincluding a cannabinoid acid; decarboxylating at least a portion of thecannabinoid acid by applying an elevated temperature to the material,thereby increasing a rate of decarboxylation; detecting, with a firstsensor having an output, carbon dioxide released during decarboxylation;and, processing the first sensor output to determine whetherdecarboxylation is complete to within a threshold in the providedmaterial. 17) The method of claim 16 wherein: the first sensor having anoutput provides a measure of carbon dioxide concentration; and, the stepof processing the first sensor output to determine whetherdecarboxylation is complete to within a threshold comprises comparingthe measure of carbon dioxide concentration with a threshold. 18) Themethod of claim 17 further including a step selected from the followinglist: halting the application of elevated temperature to the materialwhen decarboxylation is complete to within a threshold; or, providing anindication of completeness. 19) The method of claim 17 wherein thethreshold is approximately 500 parts-per-million of carbon dioxide. 20)The method of claim 16 further including a step of: detecting, with asecond sensor having an output, carbon dioxide at a second location, thesecond location being distinct from the location of the first sensor;and, wherein the step of processing the first sensor output to determinewhether decarboxylation is complete to within a threshold in theprovided material further includes processing the second sensor outputin combination with the first sensor output to determine whetherdecarboxylation is complete to within a threshold in the providedmaterial.